When and where did her husband die?
Burial ground records are mostly in the care of the local authority, in this case now North Lanarkshire Council. Suggest asking them. In the event that it could be in a cemetery they don't manage, they will know who does manage it.https://www.northlanarkshire.gov.uk/births-marriages-and-deaths/deaths/cemeteries/cemeteries-service
She may be buried in Airdrie, but in a churchyard that the records no longer exist.